There is frequently a need to couple RF devices together with minimal loss. A mechanical connector is typically employed for such a connection. There are many circumstances where a mechanical connector is impractical, or mechanical variability in the position of the connector is desirable.
The typical approach is to use a specialized mechanical connector that that has spring loaded centering rings to initially align the connectors and allow them to move around after mating. One drawback with such specialized connectors is that they are both expensive and the mechanical structures required to permit movement make the entire assembly cumbersome.
Another approach is to use contactless coupling devices. Existing contactless devices typically include coupling members that are magnetically coupled together to transfer energy between the coupling members.
One of the drawbacks with existing contactless coupling devices that include magnetically coupled members is that magnetic coupling devices usually require some sort of magnetic core, such as a ferrite core, in order to contain the magnetic flux and thereby minimize insertion loss. Magnetic coupling devices can also be quite large if they are intended to couple low frequency signals and the magnetic core material can add substantially to the size and weight of the coupler.
A related type of magnetic coupler is a transmission line coupler. This type of coupler usually operates over a limited range of frequencies and requires a relatively long coupling region in order to achieve low loss coupling.